Frameless radiosurgery treatment system and method

ABSTRACT

A method of compensating for breathing and other motions of a patient during treatment includes periodically generating internal positional data about an internal target region. The method further includes generating external positional data about external motion of the patient&#39;s body using an external sensor and generating a correlation between one or more positions of the internal target region and one or more positions of an external region using the external positional data of the external sensor and the internal positional data of the internal target region. The method further includes predicting the position of the internal target region at some later time based on the correlation model.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 13/306,951, filed Nov. 29, 2011 and entitled “Frameless Radiosurgery Treatment System and Method,” which is a continuation of U.S. patent application Ser. No. 12/356,442, filed Jan. 20, 2009 and entitled “Frameless Radiosurgery Treatment System and Method,” issued Dec. 27, 2011 as U.S. Pat. No. 8,086,299, which is a continuation of U.S. patent application Ser. No. 10/919,765, filed Aug. 17, 2004 and entitled “Frameless Radiosurgery Treatment System and Method,” now abandoned, which is a continuation of U.S. patent application Ser. No. 09/663,104, filed Sep. 15, 2000 and entitled “Frameless Radiosurgery Treatment System and Method,” issued Aug. 17, 2004 as U.S. Pat. No. 6,778,850, which is a continuation in part of U.S. patent application Ser No. 09/270,404, filed Mar. 16, 1999 and entitled “Apparatus and Method for Compensating for Respiratory and Patient Motion During Treatment,” issued Nov. 7, 2000 as U.S. Pat. No. 6,144,875, all of which are owned by the same assignee as the present application and all of which are incorporated herein by reference.

BACKGROUND

This invention relates generally to a system and method for treating a patient and in particular to a system and method for controlling a treatment to administer a precise dose to a patient. In more detail, the invention relates to an apparatus and method for performing accurate surgical procedures on a particular target region within a patient utilizing previously obtained reference data indicating the position of the target region with respect to its surrounding which may contain certain reference points.

In order to control a surgical procedure, such as radiosurgery, many different prior techniques have been used including the manual targeting of the treatment. Many of the prior techniques are not sufficiently accurate so that healthy tissue surrounding the target region is often unnecessarily irradiated and damaged or killed. Other techniques are clumsy and cannot be used for particular types of treatments. For example, one prior technique involved frame-based stereotaxy that was often used for body parts and regions that could be easily physically immobilized. For example, the frame based stereotaxy was often used to immobilize the head of the patient so that a target region in the brain, such as a brain tumor, could be irradiated by the radiosurgical beam. To do so, the patient was positioned on a treatment bed and then his/her head was immobilized by a frame that was securely attached to the person's head with some attachment means and that was also securely attached to an immovable object such as a treatment table. Thus, during the treatment, the patient was not able to move his/her head at all which permitted an accurate targeting of the treatment. The problem is that a frame-based system cannot be used for fractionated treatment in which repeated smaller does are given to the patient over some predetermined period of time, such as a couple of weeks or a month. A fractionated treatment plan is often desirable since it permits larger overall doses of treatment, such as radiation, to be applied to the target region while still permitting the healthy tissue to heal. Clearly, it is extremely difficult to leave the frame secured to the patient's head for that period of time. In addition, it is impossible to remove the frame and later reposition the frame in the exact same location for the next treatment. Thus, the frame based stereotaxy provides the desired accuracy, but cannot be used with various desirable treatment schedules.

Another typical positioning system is a frameless stereotaxy system wherein a physical frame attached to the patient is not necessary. An example of a frameless stereotaxy system is disclosed in U.S. Pat. No. 5,207,223 which is owned by the same assignee as the present application and is incorporated herein by reference. In general, a preoperative imaging of the region surrounding the target region is completed, such as by computer tomography. Then, during the treatment, a stereo image is generated, such as by X-ray imaging. The stereo image is then correlated to the preoperative image in order to locate the target region accurately. Then, a radiation source located on a robot is automatically positioned based on the correlation between the preoperative scans and the stereo images in order to accurately treat the target region without -unnecessarily damaging the healthy tissue surrounding the target region.

The current frameless stereotaxic techniques have some limitations which limit their effectiveness. First, most surgical operation rooms have limited workspace and the current stereotaxic frameless systems require a large space due to the movement of the robot supporting the surgical radiation beam and the two beam imagers Second, the cost of having two beam generators and two imagers is very high making the treatment system very expensive These systems also typically require some form of implanted fiducials, such as markers that are viewable using an X-ray, to track soft tissue targets. Finally, for most current frameless systems, breathing and other patient motion may interfere with the target region identification and tracking due to a degradation of the images. Thus, it is desirable to provide a frameless radiosurgery treatment system and method that overcomes the above limitations and problems and it is to this end that the present application is directed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a typical frameless radiosurgical treatment system;

FIG. 2 is a diagram illustrating the diagnostic and treatment beams of the system shown in FIG. 1;

FIG. 3 is a block diagram illustrating the treatment system of FIG. 1;

FIG. 4 is a diagram illustrating a preferred embodiment of the frameless treatment system in accordance with the invention;

FIG. 5 is a block diagram illustrating more of the details of the treatment system of FIG. 4;

FIG. 6 is a flowchart illustrating a method for treatment in accordance with the invention using the system of FIG. 4;

FIG. 7 is a diagram illustration a respiration cycle of a patient;

FIG. 8 is a flowchart illustrating a method for treating a patient with respiration tracking in accordance with the invention;

FIG. 9 is a diagram illustrating a second embodiment of the frameless treatment system in accordance with the invention;

FIG. 10 is a flowchart illustrating a method for treatment in accordance with the invention using the system of FIG. 9;

FIG. 11 is a diagram illustrating a third embodiment of the frameless treatment system in accordance with the invention;

FIG. 12 is a flowchart illustrating a method for treatment in accordance with the invention using the system of FIGS. 11; and

FIG. 13 illustrates the deformation of the pre-treatment and/or intra-treatment data to establish optimal correspondence to infer better target positions.

DETAILED DESCRIPTION

The invention is particularly applicable to a radiosurgical treatment system and method and it is in this context that the invention will be described. It will be appreciated, however, that the system and method in accordance with the invention has greater utility, such as to other types of treatments wherein it is necessary to accurately position a treatment at a target, region within the patient in order to avoid damaging healthy tissue such as to other types of medical procedures with other types of medical instruments, such as positioning biopsy needles, ablative, ultrasound or other focused energy treatments, positioning a laser beam for laser beam treatment or positioning radioactive seeds for brachytherapy. Prior to describing the invention, a typical radiosurgery device will be described to provide a better understanding of the invention.

FIGS. 1-3 are diagram illustrating an example of a stereotaxic radiation treatment device 10. The radiation treatment device 10 may include a data processor 12, such as a microprocessor, and a disc or tape storage unit 13 (shown in FIG. 3) which may store a three dimensional image of a patient 14. The three dimensional image may be loaded into the data processor, if not already there, to compare the three dimensional image to images generated during the surgical procedure. The three dimensional image may be generated by various conventional techniques such as computer aided tomography (CAT) scan or magnetic resonance imaging (MR). The radiation treatment device 10 may also include a beaming apparatus 20 which, when activated, emits a collimated surgical ionizing beam directed at a target region 18 (shown in FIG. 2). The collimated surgical ionizing beam may have sufficient strength to cause the target region to become necrotic. A variety of different beaming apparatus may be used which generate an ionizing radiation or heavy particle beam such as a linear accelerator and preferably an x-ray linear accelerator. Such an x-ray beaming apparatus is commercially available. The beaming apparatus may be activated by the operator throwing a switch 23 at a control console 24 connected to the beaming apparatus 20 by a cable 22.

The radiation treatment device 10 may also include an apparatus for passing a first diagnostic beam 26 and a second diagnostic beam 28 through the region previously imaged by the three-dimensional image. The diagnostic beams are positioned at a predetermined non-zero angle with respect to each other, such as being orthogonal as shown in FIG. 2. The diagnostic beams may be generated by a first x-ray generator 30 and a second x-ray generator 32, respectively. A first and second image receiver 34, 36 or a single receiver may receive the diagnostic beams 26, 28 to generate an image from the diagnostic beams which is fed into the microprocessor 12 (as shown in FIG. 4) so that the diagnostic images may be compared to the three-dimensional image.

The radiation treatment device 10 may also include a device for adjusting the relative positions of the beaming apparatus 20 and/or the patient 14 so that the ionizing beam is continuously focused on the target region 18. In the radiation treatment device shown in FIG. 1, the positions of the beaming apparatus and the patient may be altered with six degrees of freedom by a gantry 40 and a moveable operating table 38 with a tilting top 44. The positions of the beaming apparatus relative to the patient may also be accomplished by using a processor controllable robotic arm mechanism that permits the beaming apparatus to be moved freely about the patient's body including up, down, longitudinally along or laterally along the body of the patient.

FIG. 3 is a block diagram of the radiation treatment device 10 including the microprocessor 12, the tape drive 13, the beaming apparatus 20, the robotic ann. 46 or the gantry 40, the x-ray cameras 30, 32, 34 and 36, and the operator control console 24 as described above. In addition, the device 10 may include safety interlocks 50 to ensure that the beaming apparatus is not activated accidentally. The device 10 may also include an operator display 48 for tracking the progress of the treatment and controlling the treatment. Any further details of the radiosurgery device may be found in U.S. Pat. No. 5,207,223 which is owned by the assignee of this application and which is incorporated herein by reference.

The above system is well suited for the treatment of stationary target regions (e.g., stationary with respect to bony structures that can be seen on an image) wherein respiratory motion or pulsation motion do not affect the accuracy of the treatment beam. The drawback of the above system is that anatomic sites subject to respiratory motion are difficult to treat. In accordance with the invention, the frameless treatment system may improve upon the system shown in FIGS. 1-3. The frameless treatment system and method in accordance with the invention with the above advantages will now be described.

FIG. 4 is a diagram illustrating a preferred embodiment of the frameless treatment system 180 in accordance with the invention. This embodiment of the invention is particular applicable to the targeting of a target region without embedded markers wherein there is no surrounding region that can be easily located (e.g., no bones are present) and respiration motion may affect the position of the target region. An example of a target region for this embodiment is a lung tumor.

The treatment system 180 may include a patient treatment table or couch 102 on which a patient 103 may rest during the treatment. The treatment system may also include a diagnostic beam recording device 104 that may be located underneath the treatment table and underneath the patient and one or more diagnostic beam generators 106 (one is shown in this example). The recording device 104 may record the images generated when the diagnostic beam device is energized at one or more different predetermined positions. The recording device 104 may be any device that can be used to capture the image generated by the diagnostic beams. In a preferred embodiment, the recording device 104 may be the amorphous silicon plate that captures the x-ray beams being generated by the diagnostic beam generators 106. The recording device 104 may be connected to a computer that controls the operation of the recording device and the diagnostic beam generator. The recording device in this embodiment may also have a first portion 105 and a second portion 107 wherein the first diagnostic beam is captured by the first portion and the second diagnostic beam is captured by the second portion. Thus, the diagnostic beams may be simultaneously energized or may be sequentially energized. A recording medium with one or more diagnostic beams is also shown in U.S. Pat. No. 5,207,223 to Adler which is owned by the same assignee as the present invention.

The robot and the treatment beam generator (shown in FIG. 5) are not shown in FIG. 4. The system may further include a track 152 in which the diagnostic beam generator moves so that the diagnostic beam generator may be moved to different positions (see the diagnostic beam generator 106 in a first position 154 and the other positions shown by the phantom pictures of the generator) wherein the diagnostic beam generator is at a different non-zero angle with respect to the other positions. Thus, in this embodiment, the diagnostic beam generator 106 is moved from the first position 154 to other positions at periodic times in order to generate the images of the target region as described above. In addition to the elements shown in FIG. 5, the system may also include a controller, to position of the diagnostic beam generator, that may be controlled by the computer.

In addition to the above, this system 180 may also include an external marker tracking device 182 that may include one or more external marker tracking generators 184 that generate one or more external marker tracking beams 184, such as infrared beams or passive markers whose position is detectable with optical cameras. The system may also include one or more external markers 188 attached to the patient that measure the external movement of the patient during respiratory motion as described in more detail in the co-pending application that was incorporated by reference. Now, the system will be described in more detail.

FIG. 5 is a block diagram illustrating more of the details of the treatment system 100 of FIG. 4. In particular, the system 100 may include a computer 110 that controls the operation of the various elements of the system including the beam generators 106, 108 as well as the image recorder 104. The system may also include a treatment beam device 112, such as a linear accelerator (LINAC) in this embodiment, that generates a treatment beam and a robot 114 that positions the treatment beam (a LINAC manipulator in this embodiment) that are both controlled by the computer 110 that may be a multi-processor computer in this embodiment. The computer may issue control commands and receive back status commands from the treatment beam generator 112, the robot 114 and the beam generators 106, 108. For the image recorder 104, the computer may issue control signals to control the operation of the image recorder as described above and may receive image data from the image recorder.

The system may also include safety interlocks 116 that ensures that the diagnostic beams and the treatment beam cannot be activated (the beams are only energized when a status signal is received by the computer) unless all people other than the patient are out of the treatment room due to the radiation danger. The system may also include a tape drive 118 for storing the images generated by the image recorder, the pre-operative CT three-dimensional images and any treatment planning software that may perform the comparison of the images and control the movement of the treatment beam. The system may further include an operator control console 120 and an operator display 122 that permit a user of the system, such as a surgeon, to interact with and operate the system and monitor the treatment. The treatment planning software in the computer may compare the pre-operative image to the images from the diagnostic beam generators to determine how to control the treatment robot and therefore the treatment beam during the treatment. The computer, based on the comparison and the surgeon's manual commands, may then control the treatment beam in order to deliver the appropriate dose to the patient without damaging the healthy tissue surrounding the target region. Now, a method of treatment using the preferred embodiment will be described.

FIG. 6 is a flowchart illustrating a method 200 for treatment in accordance with the invention using the system of FIG. 4. In step 202, a three-dimensional mapping of a region of the patient including the target region is generated prior to the treatment. The three-dimensional mapping may be done using typical equipment such as computer tomography, magnetic resonance tomography or the like. The three-dimensional mapping of the region is stored in the storage device 118. The mapping shows the relative locations of the target region with respect to other surrounding regions that may be seen in the mapping to locate the target region relative to the surrounding regions. For example, the target region may be a lung tumor.

On the day of treatment, the patient may be positioned on the treatment bed as shown in FIG. 9. The respiratory cycle of the patient may then be determined in step 203 and at various different times during the treatment. The respiratory cycle may be determined by monitoring chest wall surface movement with optical or ultrasound digitizers, and/or by using a strain gauge, by the measurement of the airflow exiting the patient or by other well known methods. In step 204, the system may determine if the treatment can begin based on the status of the safety interlocks. If it is not safe to begin the treatment, then the method loops back to test the safety interlocks until a safe condition is indicated.

In step 206, a diagnostic beam generator is positioned along the track in the appropriate position and energized by the computer in order to generate an image on the recording device. In a preferred embodiment, the diagnostic beam generator is an x-ray generators and the image recorder is an amorphous silicon imager that generates an image in response to x-rays as is well known. The image generated by the first diagnostic beam in the image recorder may then be downloaded by the computer to the storage device attached to the computer in step 208 and the image recorder may be reset. Each image is acquired at the same phase of the respiratory cycle 20 as described below with respect to FIGS. 7 and 8.

In step 210, the method determines if there are any other positions for the diagnostic beam. If there are other positions for the diagnostic beam, the method loops back to step 206 to energize that generator at the other position, generate an image and download the image to the storage device. In this embodiment, the movement of the diagnostic beam generator along the track generates multiple images wherein each image is at a non-zero angle with respect to the other images and acquired during the same phase of the respiratory cycle. In accordance with the invention, the method sequentially energizes the diagnostic beam generator at different positions to generate the images in a sequential manner. In accordance with the invention, repeated sequence of images from the diagnostic beam generator may be generated at periodic times so that the location of the target region at different times may be determined.

The series of diagnostic beam images may be processed using a CT-like algorithm to generate a 3-D image of the patient during the treatment. Once the series of diagnostic images are processed into a 3-D image, the 3-D image is compared to the three-dimensional preoperative mapping as is well known to determine the location of the target region at the particular time in step 212. In step 214, the targeting of the treatment beam is adjusted based on the comparison so that the treatment beam is always focused on the target region. If there are repeated diagnostic images generated, after each new set of images is generated, the images are compared to the mapping and the treatment beam targeting is adjusted to compensate for changes in the position of the target region. In this manner, the target region is accurately tracked so that the treatment beam is focused on the target region.

In some cases, the placement of certain structures is visible in the intra-treatment 3-D reconstruction, but the target region or critical region is either not visible at all, not clearly visible, or is visible but difficult to segment automatically by computer. In this case, the system may comprise the step of deforming the intra-treatment images in such a way that the positions of the clearly visible structures best match the pre-operative image data. From this, the exact deformation pattern of the entire anatomical area can be inferred. The exact position of the target and/or healthy critical tissue visible in the pre-operative image data, but not clearly visible in the intra-treatment data may be inferred as described in more detail with reference to FIG. 13.

FIG. 7 is a chart 260 illustrating a typical respiration cycle for a human being wherein the respiration cycle is represented by a sine wave. The y-axis of the chart is the movement of the chest wall thus showing that the chest wall moves out and in during the respiration cycle. A first point 262 in the respiration cycle with maximum expansion of the chest and a second point 264 in the respiration cycle with no chest movement are shown. The respiration cycle may be determined using the various techniques described above. In accordance with the invention, the energizing of the diagnostic beams and the treatment beam may be periodically timed so that the energizing occurs at the corresponding points in the respiration cycle such as at the first point or the second point. In addition, the energizing of the beams may occur at more than one time during the respiration cycle. Thus, the accuracy of the treatment is improved since the beams are energized at the same time in the respiration cycle.

FIG. 8 is a flowchart illustration of a method 270 for energizing a diagnostic or treatment beam based on the respiration cycle in accordance with the invention. In step 272, the treatment is started and the respiration cycle of the patient is determined. In step 274, the system determines if at predetermined point in the respiration cycle has occurred and waits until the predetermined point has occurred. Once the predetermined point in the respiration cycle is reached, the system may energize the beam in step 276. Now, a second embodiment of the invention will be described.

FIG. 9 is a diagram illustrating a second embodiment of the frameless treatment system 150 in accordance with the invention. This embodiment of the invention is particular applicable to fiducial-less targeting of a target region wherein a surrounding region can be located, but the surrounding region does not have a fixed relationship with the target region (e.g., no bones are present) and respiration motion does not affect the position of the target region. An example of a target region for this embodiment is the prostate.

The system 150 may include the same elements as the prior embodiment as designated by like reference numerals such as the treatment table 102, the image recorder 104 and the diagnostic beam generator 106. As with the prior embodiment, the robot and the treatment beam generator are not shown. In this embodiment, a single diagnostic beam generator 106 may be used to further reduce the cost of the treatment system. In this embodiment, the system may further include a track 152 in which the diagnostic beam generator moves so that the diagnostic beam generator may be moved to different positions (see the diagnostic beam generator 106 in a first position 154 and the other positions shown by the phantom pictures of the generator) wherein the diagnostic beam generator is at a different non-zero angle with respect to the other positions. Thus, in this embodiment, the diagnostic beam generator 106 is moved from the first position 154 to other positions at periodic times in order to generate the images of the target region as described above. The embodiment may have similar elements as those shown in FIG. 5 and may also include a controller, to position the diagnostic beam generator, that may be controlled by the computer. Now, the method of treatment using the second embodiment will be described.

FIG. 10 is a flowchart illustrating a method 160 for treatment in accordance with the invention using the system of FIG. 9. In step 162, a three-dimensional mapping of a region of the patient including the target region is generated prior to the treatment. The three-dimensional mapping may be done using typical equipment such as computer tomography or the like. The three-dimensional mapping of the region is stored in the storage device 118. The mapping shows the location of the target region with respect to other surrounding regions that may be seen in the mapping to locate the target region relative to the surrounding regions. For example, the target region may be a prostate tumor and the other surrounding regions may be the bladder. On the day of treatment, the patient may be positioned on the treatment bed as shown in FIG. 7. In step 164, the system may determine if the treatment can begin based on the status of the safety interlocks. If it is not safe to begin the treatment, then the method loops back to test the safety interlocks until a safe condition is indicated.

In step 166, a diagnostic beam generator is positioned along the track in the appropriate position and energized by the computer in order to generate an image on the recording device. In a preferred embodiment, the diagnostic beam generators is an x-ray generator and the image recorder is an amorphous silicon imager that generates an image in response to x-rays as is well known. The image generated by the first diagnostic beam in the image recorder may then be downloaded by the computer to the storage device attached to the computer in step 168 and the image recorder may be reset. In step 170, the method determines if there are any other positions for the diagnostic beam. If there are other positions for the diagnostic beam, the method loops back to step 166 to energize that generator at the other position, generate an image and download the image to the storage device. In this embodiment, the movement of the diagnostic beam generator along the track generates multiple images wherein each image is at a non-zero angle with respect to the other images. In accordance with the invention, the method sequentially energizes the diagnostic beam generator at different positions to generate the images in a time sequential manner. In accordance with the invention, repeated sequence of images from the diagnostic beam generator may be generated at periodic times so that the location of the target region at different times may be determined. The 2-D images generated by the diagnostic beams are processed to yield a CT-like image which may then be compared to the pre-operative 3-D mapping.

Once the diagnostic images are generated, the two or more images are compared to the three-dimensional pre-operative mapping as is well known to determine the location of the target region at the particular time in step 172. The comparison may again include the step of deformation as described above. In step 174, the targeting of the treatment beam is adjusted based on the comparison so that the treatment beam is always focused on the target region. If there are repeated diagnostic images generated, after each new set of images is generated, the images are compared to the mapping and the treatment beam targeting is adjusted to compensate for changes in the position of the target region. In this manner, the target region is accurately tracked so that the treatment beam is focused on the target region.

FIG. 11 is a diagram illustrating another embodiment of the frameless treatment system 100 in accordance with the invention that may be particularly suited for treating target regions that have a fixed relationship to a fixed reference point, such as bones. Thus, this embodiment of the invention may be used for treating, for example, the spine of a patient or the brain of the patient since these target regions are near or surrounded by bones. The other embodiments of the invention described below may be particularly suited for the treatment of other target regions. In this figure, only one detector under the patient couch is used. The two diagnostic beams in this case may either be activated sequentially or the two beams may be activated simultaneously while projecting their respective images to a different portion of the single detector plate/camera. The simultaneous activation of the diagnostic beams is particularly useful when time-stamps are needed so that the exact time of a given 3-D position is known.

The treatment system 100 may include a patient treatment table or couch 102 on which a patient 103 may rest during the treatment. In the example shown, the brain of the patient is being treated. The treatment system may also include a diagnostic beam recording device 104 that may be located underneath the treatment table and underneath the patient and one or more diagnostic beam generators 106, 108 (two are shown in this example). The recording device 104 may record the images generated when each diagnostic beam device 106, 108 is energized. The recording device 104 may be any device that can be used to capture the image generated by the diagnostic beams. In a preferred embodiment, the recording device 104 may be the amorphous silicon plate that captures the x-ray beams being generated by the diagnostic beam generators 106, 108. The recording device 104 may be connected to a computer that controls the operation of the recording device and the diagnostic beam generators. The recording device in this embodiment may have a first portion 105 and a second portion 107 wherein the first diagnostic beam is captured by the first portion and the second diagnostic beam is captured by the second portion. Thus, the diagnostic beams may be simultaneously energized or may be sequentially energized.

In accordance with the invention, the diagnostic beam generators 106, 108 may be controlled by the computer to be energized at different predetermined time intervals or simultaneously so that each diagnostic beam generator is producing an image on the recording device at a different time or simultaneously. In addition, the diagnostic beam generators are located at different positions so that the diagnostic beams pass through the patient at different non-zero angles so that the angle between the two diagnostic beams is also non-zero which permits a two-dimensional image of the target region to be generated from the two images.

In operation, the first diagnostic beam generator 106 may be energized to emit a diagnostic beam that passes through the target region and generates an image on the recording device. The image developed by the recording device is then downloaded to the computer and the recording device is erased. Next, the second diagnostic beam 108 is energized and an image generated by the second diagnostic beam is received by the recording device. This image is also downloaded to the computer where it is stored with the first image. By comparing these diagnostic images in combination with the pre-operative 3-D CT scan or the like, the treatment beam (not shown) of the treatment system may be accurately targeted at the target region. For purposes of illustration, the treatment beam generator and the treatment beam robot are not shown in FIG. 11. The operation of this embodiment of the treatment system is described in more detail below with reference to FIG. 12.

FIG. 12 is a flowchart illustrating a method 130 for treatment in accordance with the invention using the system of FIG. 11. In particular, in step 132, a three-dimensional mapping of a region of the patient including the target region is generated prior to the treatment. The three-dimensional mapping may be done using typical equipment such as computer tomography or the like. The three-dimensional mapping of the region is stored in the storage device 118. The mapping shows the location of the target region with respect to other surrounding regions that may be seen in the mapping and appear on X-ray images made with the image recorder. For example, the target region may be a brain tumor and the other surrounding regions may be the skull bones. On the day of treatment, the patient may be positioned on the treatment bed as shown in FIG. 4. In step 134, the system may determine if the treatment can begin based on the status of the safety interlocks. If it is not safe to begin the treatment, then the method loops back to test the safety interlocks until a safe condition is indicated.

In step 136 when the treatment begins, a first diagnostic beam generator is energized by the computer in order to generate an image on the recording device. In a preferred embodiment, the diagnostic beam generators are x-ray generators and the image recorder is an amorphous silicon imager that generates an image in response to x-rays as is well known. The image generated by the first diagnostic beam in the image recorder may then be downloaded by the computer to the storage device attached to the computer in step 138 and the image recorder may be reset. In step 140, the method determines if there are any other diagnostic beams to be energized. If there are other diagnostic beams to energize, the method loops back to step 136 to energize that generator, generate an image and download the image to the storage device. In this embodiment, there may be two diagnostic beam generators that are at a predetermined non-zero angle with respect to each other. In accordance with the invention, the method sequentially energizes the diagnostic beam generators to generate the images from each of the diagnostic beams in a time sequential manner. In accordance with the invention, repeated pairs of images from the diagnostic beam generators may be generated at periodic times so that the location of the target region at different times may be determined.

Once the diagnostic images are generated, the two images are compared to the three-dimensional pre-operative mapping as is well known to determine the location of the target region at the particular time in step 142. In step 144, the targeting of the treatment beam is adjusted based on the comparison so that the treatment beam is always focused on the target region. If there are repeated diagnostic images generated, after each new set of images is generated, the images are compared to the mapping and the treatment beam targeting is adjusted to compensate for changes in the position of the target region. In this manner, the target region is accurately tracked so that the treatment beam is focused on the target region.

FIG. 13 illustrates a pre-operative image 250 and intra-treatment image data 252 generated by the diagnostic beams. As shown, the intra-treatment images generated by the diagnostic beams are less clear and it is difficult to make out all of the structures or even the target region in the image. The pre-operative image 250, on the other hand, is very clear and each structure of the body can be clearly seen. Therefore, in order to make it possible to infer the position of the target region from the intra-treatment images shown, the intra-treatment image is deformed, using various well known deformation techniques such as linear interpolation or warping, to form a deformed image 254 until the intra-treatment images and its structures form the best match with the pre-operative images. Once the deformation is completed, the position of the target region may be inferred from the position of the structures. This deformation technique may be used with all of the embodiments of the invention described above.

Although the above embodiments show a single diagnostic beam source being used, the invention is not limited to a single diagnostic beam source. In fact, the system may use five fixed sources that generate the diagnostic beams and two or more moving sources that generate the diagnostic beams. For the fixed sources, they may be activated at specific time points throughout the respiration cycle. More detailed information about the deformation model corresponding to respiratory motion may then be obtained as set forth in the U.S. patent application Ser. No. 09/270,404.

While the foregoing has been with reference to particular embodiments of the invention, it will be appreciated by those skilled in the art that changes in these embodiments may be made without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims. 

What is claimed is:
 1. A method comprising: generating internal positional data about an internal target region in a patient at a first frequency; generating external positional data about motion of an external region of the patient's body using an external sensor at a second frequency that is greater than the first frequency; determining a correlation between one or more positions of the internal target region and one or more positions of the external region using the external positional data of the external sensor and the internal positional data of the internal target region; and predicting a future position of the internal target region based on the determined correlation.
 2. The method of claim 1, wherein the internal positional data identifies internal motion of the patient's body, the internal motion comprising motion of the internal target region.
 3. The method of claim 1, further comprising: generating a series of preoperative images for both the internal target region and the external region of the patient's body; and generating an initial correlation model based on the series of preoperative images prior to treatment of the patient.
 4. The method of claim 3, further comprising: generating new internal positional data and new external positional data during the treatment; and updating the initial correlation model during the treatment by recomputing the initial correlation model based on the new internal positional data and the new external positional data.
 5. The method of claim 1, further comprising: gating the treatment based on a correlation model generated from the correlation so that the treatment is switched on and off periodically.
 6. The method of claim 1, wherein the internal positional data comprises data for one or more fiducial markers located near the internal target region, the method further comprising: generating a correlation model from the correlation based on computing a deformation state of the internal target region based on relative positions of the one or more fiducial markers.
 7. The method of claim 1 further comprising: moving a treatment beam based on the correlation.
 8. The method of claim 1 further comprising: moving a collimating device to change characteristics of a treatment beam based on the correlation.
 9. An apparatus, comprising: a first detection device to generate internal positional data about an internal target region in a patient at a first frequency; a second detection device to generate external positional data about motion of an external region of the patient's body using an external sensor at a second frequency that is greater than the first frequency; and a processor, coupled to the first detection device and to the second detection device, configured to: determine a correlation between one or more positions of the internal target region and one or more positions of the external region using the external positional data of the external sensor and the internal positional data of the internal target region; and predict a future position of the internal target region based on the determined correlation.
 10. The apparatus of claim 9, further comprising: a treatment beam generator, coupled to the processor, to generate a treatment beam, the treatment beam generator having a gating element that switches on and off the treatment beam periodically based on the correlation.
 11. The apparatus of claim 9, wherein: the internal positional data comprises data for one or more fiducial markers located near the internal target region; and the processor is to generate a correlation model from the correlation based on computing a deformation state of the internal target region based on relative positions of the one or more fiducial markers.
 12. The apparatus of claim 9, further comprising: a treatment beam generator, coupled to the processor, to generate a treatment beam, wherein the treatment beam generator moves the treatment beam in accordance with the correlation.
 13. The apparatus of claim 9, further comprising: a treatment beam generator, coupled to the processor, to generate a treatment beam; and a collimating device, coupled to the treatment beam generator, to change characteristics of the treatment beam based on the correlation.
 14. The apparatus of claim 9, wherein the processor is further configured to generate a correlation model based on the correlation and to update the correlation model during treatment by recomputing the correlation model based on new internal positional data and new external positional data.
 15. A non-transitory computer readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform operations comprising: receiving, by the processor, internal positional data about an internal target region in a patient, the internal positional data having been generated at a first frequency; receiving, by the processor, external positional data about motion of an external region of the patient's body, the external positional data having been generated, using an external sensor, at a second frequency that is greater than the first frequency; determining, by the processor, a correlation between one or more positions of the internal target region and one or more positions of the external region using the external positional data of the external sensor and the internal positional data of the internal target region; and predicting, by the processor, a future position of the internal target region based on the determined correlation.
 16. The non-transitory computer readable storage medium of claim 15, wherein the internal positional data identifies internal motion of the patient's body, the internal motion comprising motion of the internal target region.
 17. The non-transitory computer readable storage medium of claim 15, the operations further comprising: receiving a series of preoperative images for both the internal target region and the external region of the patient's body; and generating an initial correlation model based on the series of preoperative images prior to treatment of the patient.
 18. The non-transitory computer readable storage medium of claim 17, the operations further comprising: receiving new internal positional data and new external positional data during the treatment; and updating the initial correlation model during the treatment by recomputing the initial correlation model based on the new internal positional data and the new external positional data.
 19. The non-transitory computer readable storage medium of claim 15, the operations further comprising: gating the treatment based on a correlation model generated from the correlation so that the treatment is switched on and off periodically.
 20. The non-transitory computer readable storage medium of claim 15, further comprising: performing at least one of a) moving a treatment beam based on the correlation or b) moving a collimating device to change characteristics of a treatment beam based on the correlation. 